Extended Forecast Discussion NWS Weather Prediction Center College Park MD 243 AM EDT Sat Oct 01 2022 Valid 12Z Tue Oct 04 2022 - 12Z Sat Oct 08 2022 ...Overview... A wavy pattern should be in place by the start of the medium range period on Tuesday, with a compact upper low over the East and shortwave moving through the High Plains. By later in the week, large scale troughing looks to amplify over the East as upper level ridging builds over the West with this general pattern remaining mostly stagnant into next weekend. The period looks rather quiet in terms of any significant sensible weather threats, with heavy rains/gusty winds moving offshore the Mid-Atlantic Tuesday-Wednesday (likely in some form the remnants of currently Post-T.C. Ian). Monsoon moisture into the Southwest, associated with weak energy over the region, will continue through much of the period as well. ...Guidance Evaluation/Predictability Assessment... Besides some lingering uncertainties in the details of individual systems, the latest suite of guidance shows above average agreement through much of the period. A general blend of the latest deterministic models worked well through day 5. By later in the period, there are some more noticeable differences which arise concerning individual shortwaves riding down the east side of the ridge into the long-wave troughing over the East. Incorporating modest amounts of the ensemble means for days 6 and 7 seemed to tone down these harder to resolve differences and provide a reasonable overall pattern depiction. The QPF in the medium range was based largely on the 01/01z National Blend of Models, with some incorporation of mainly the GFS and ECMWF across the Southwest and also the northern Plains-Upper Midwest-Great Lakes to provide a bit larger of a QPF footprint in these locations than what was depicted by the too light NBM, which is a known bias. Overall, this approach maintained good continuity with the previous WPC forecast as well. ...Weather/Hazards Highlights... The potentially slow moving eastern U.S. upper low and associated low pressure (whether initially from Ian or eventual redevelopment just off the East Coast) may continue to produce some rainfall and gusty winds along the Northeast coast, though models agree the heaviest rainfall should remain offshore. Elsewhere, monsoonal moisture into the Southwest will drive some diurnal showers and thunderstorms into Thursday, with locally heavy rain in some locations possible. A cold front shifting from the Northern Plains to the Upper Midwest and Great Lakes should result in just some widespread showers through the region as the front moves through. Initially below normal temperatures along the East Coast should trend back towards normal by the middle of next week and temperatures out west trend much warmer underneath of a blocky upper ridge. Daytime highs over the Northwest could be 10 to 15 degrees above normal into next weekend, though the resulting temperature values aren't likely to create any heat related hazards. Canadian high pressure spilling into the north-central U.S. and expanding eastward will result in much below normal temperatures shifting from the northern Plains into the Upper Midwest and the Northeast Thursday-Saturday. Daytime highs in some locations could be 15 to 20 degrees below normal with overnight temperatures dropping into the 30s (or lower in far northern areas) for many. Santorelli Additional 3-7 Day Hazard information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php WPC medium range 500mb heights, surface systems, weather grids, quantitative precipitation, experimental excessive rainfall outlook, winter weather outlook probabilities and heat indices are at: https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml https://www.wpc.ncep.noaa.gov/#page=ero https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4 https://www.wpc.ncep.noaa.gov/heat_index.shtml